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remotely like that. That feeling is what draws us and holds us, what
pins us to one another for that long moment. It just feels so good. For
most of us, that is reason enough for human sexual intercourse. But for
biologists, that reason isn’t quite enough. Somewhere in the warp of
the cerebral cortices of these curious few, there remains an unanswered
question: Why does sex feel so good?
After decades of cogitation, not to mention extensive experimentation, most biologists agree that sex feels so very good because sex creates more biologists. (Well, and others too, of course.) Which is to say
that every human being alive today, as well as every nonhuman being,
is here because every one of our direct ancestors—back to lizards and
beyond—reproduced. All of them were drawn to sexual intercourse at
least long enough to make one more like themselves, often many more
like themselves. My mother, for example, came from a family of eleven;
a sexual proclivity is definitely in my genes. It is in yours as well. Reproduction is the engine that drives all of biology. The more of you there
are, the more successful you are, biologically. It’s all about domination,
and nothing dominates like sheer numbers. Reproduction provides the
means; lust provides the motivation.
As a result, when asked “What is the purpose of sex?” most of us
answer “reproduction.” Why do we have penises and scrota, vaginas,
clitorises, and uteruses? Again—for reproduction, almighty reproduction. This answer fits very nicely with our idea about two opposite sexes.
But it also leads us into that dark labyrinth that opens with the idea that
people without functional penises and vaginas and uteruses are abnormal because their genitalia aren’t reproductive.
In reality, if you look closely, you’ll find that in many species, including our own, reproduction is not the only aim of sexual interaction.
And in some species, including our own, reproduction does not even
appear to be the primary function of sexual interaction.
Among humans, in spite of our numbers, our sexual interactions
are in fact rarely reproductive. First, most women are fertile about five
or six days a month, or around 20 percent of the time. Most humans
do not restrict their sexual activity to those five or six days. And in Sex Versus Reproduction 35 women there is nothing like the outwardly visible signs of “heat” that
accompany female estrus in so many other species—nothing obvious to
help focus human sex around periods of ovulation, to pull us together
when we are most likely to produce a child. If the only purpose of sex
is reproduction, that seems like a pretty major oversight on the part of
evolution. Beyond that, even under ideal conditions, successful fertilization after intercourse occurs less than 50 percent of the time. After
that, only about 50 percent of fertilized eggs ever develop beyond the
blastula stage (reached about one week after fertilization). And only a
small proportion of those blastulas successfully implant in the uterine
wall. Then come all the dangers and pitfalls of development. Considering all of that, even by the most optimistic estimates, human sexual
intercourse results in reproduction only about 5 percent of the time.
Our phenomenal population growth rate is more a testament to our
fondness for intercourse than it is to fecundity.
Beyond that, humans spend a lot of time having sexual intercourse
when there is zero likelihood of reproduction. Between ages twenty-five
and sixty, the percent of people having sex “at least a few times a month”
only drops from 80 percent to 65 percent. But during that same period
of our lives, essentially all women and many men go from fertile to sterile. It seems that the likelihood of reproduction has little to do with the
magnetism of sexual intercourse.
If sheer numbers were the only measure of a species’ success, then everybody on this planet should model themselves after bacteria. Bacteria are
the most successful of all living species. Bacteria outweigh all other living things combined. They outnumber us by unimaginable factors. Bacteria are found in more places on the planet than any other living thing.
There are more species of bacteria than all other species combined. And
bacteria have had a greater impact on this planet than humans can ever
hope to. Bacteria are number one. But bacteria reproduce by dividing—no sex, no lust, no titillation. Sexless cell division has pushed bacteria to the pinnacle of all biology. So it seems we, as a species, would 36 Between XX and XY be a lot better off if we reproduced asexually, like bacteria, periodically
splitting off another one like ourselves to carry our genetic heritage into
the future. Among species that reproduce asexually, every individual is
female, and every individual can produce offspring. Taking their lead
from bacteria, starfish do it, sponges do it, some worms do it, a lot of
insects do it, and sometimes even turkeys do it. Somewhere around
1952, some folks in Beltsville, Maryland, noticed that about 16 percent
of their turkey eggs developed, without fertilization, into brand-new
hens. From those hens, the turkey ranchers dev...
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This document was uploaded on 02/04/2014.
- Spring '14